2 % (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
4 \section[CoreRules]{Transformation rules}
8 RuleBase, emptyRuleBase, mkRuleBase, extendRuleBaseList,
9 unionRuleBase, pprRuleBase, ruleCheckProgram,
11 mkSpecInfo, extendSpecInfo, addSpecInfo,
12 rulesOfBinds, addIdSpecialisations,
16 lookupRule, mkLocalRule, roughTopNames
19 #include "HsVersions.h"
21 import CoreSyn -- All of it
22 import OccurAnal ( occurAnalyseExpr )
23 import CoreFVs ( exprFreeVars, exprsFreeVars, bindFreeVars, rulesRhsFreeVars )
24 import CoreUnfold ( isCheapUnfolding, unfoldingTemplate )
25 import CoreUtils ( tcEqExprX )
26 import PprCore ( pprRules )
27 import Type ( TvSubstEnv )
28 import Coercion ( coercionKind )
29 import TcType ( tcSplitTyConApp_maybe )
30 import CoreTidy ( tidyRules )
31 import Id ( Id, idUnfolding, isLocalId, isGlobalId, idName,
32 idSpecialisation, idCoreRules, setIdSpecialisation )
33 import IdInfo ( SpecInfo( SpecInfo ) )
35 import VarEnv ( IdEnv, InScopeSet, emptyTidyEnv,
36 emptyInScopeSet, mkInScopeSet, extendInScopeSetList,
37 emptyVarEnv, lookupVarEnv, extendVarEnv,
38 nukeRnEnvL, mkRnEnv2, rnOccR, rnOccL, inRnEnvR,
39 rnBndrR, rnBndr2, rnBndrL, rnBndrs2,
40 rnInScope, extendRnInScopeList, lookupRnInScope )
42 import Name ( Name, NamedThing(..), nameOccName )
44 import Unify ( ruleMatchTyX, MatchEnv(..) )
45 import BasicTypes ( Activation, CompilerPhase, isActive )
48 import Maybes ( isJust, orElse )
51 import Util ( singleton )
52 import List ( isPrefixOf )
56 %************************************************************************
58 \subsection[specialisation-IdInfo]{Specialisation info about an @Id@}
60 %************************************************************************
62 A @CoreRule@ holds details of one rule for an @Id@, which
63 includes its specialisations.
65 For example, if a rule for @f@ contains the mapping:
67 forall a b d. [Type (List a), Type b, Var d] ===> f' a b
69 then when we find an application of f to matching types, we simply replace
70 it by the matching RHS:
72 f (List Int) Bool dict ===> f' Int Bool
74 All the stuff about how many dictionaries to discard, and what types
75 to apply the specialised function to, are handled by the fact that the
76 Rule contains a template for the result of the specialisation.
78 There is one more exciting case, which is dealt with in exactly the same
79 way. If the specialised value is unboxed then it is lifted at its
80 definition site and unlifted at its uses. For example:
82 pi :: forall a. Num a => a
84 might have a specialisation
86 [Int#] ===> (case pi' of Lift pi# -> pi#)
88 where pi' :: Lift Int# is the specialised version of pi.
91 mkLocalRule :: RuleName -> Activation
92 -> Name -> [CoreBndr] -> [CoreExpr] -> CoreExpr -> CoreRule
93 -- Used to make CoreRule for an Id defined in this module
94 mkLocalRule name act fn bndrs args rhs
95 = Rule { ru_name = name, ru_fn = fn, ru_act = act,
96 ru_bndrs = bndrs, ru_args = args,
97 ru_rhs = rhs, ru_rough = roughTopNames args,
98 ru_orph = Just (nameOccName fn), ru_local = True }
101 roughTopNames :: [CoreExpr] -> [Maybe Name]
102 roughTopNames args = map roughTopName args
104 roughTopName :: CoreExpr -> Maybe Name
105 -- Find the "top" free name of an expression
106 -- a) the function in an App chain (if a GlobalId)
107 -- b) the TyCon in a type
108 -- This is used for the fast-match-check for rules;
109 -- if the top names don't match, the rest can't
110 roughTopName (Type ty) = case tcSplitTyConApp_maybe ty of
111 Just (tc,_) -> Just (getName tc)
113 roughTopName (App f a) = roughTopName f
114 roughTopName (Var f) | isGlobalId f = Just (idName f)
115 | otherwise = Nothing
116 roughTopName other = Nothing
118 ruleCantMatch :: [Maybe Name] -> [Maybe Name] -> Bool
119 -- (ruleCantMatch tpl actual) returns True only if 'actual'
120 -- definitely can't match 'tpl' by instantiating 'tpl'.
121 -- It's only a one-way match; unlike instance matching we
122 -- don't consider unification
124 -- Notice that there is no case
125 -- ruleCantMatch (Just n1 : ts) (Nothing : as) = True
126 -- Reason: a local variable 'v' in the actuals might
127 -- have an unfolding which is a global.
128 -- This quite often happens with case scrutinees.
129 ruleCantMatch (Just n1 : ts) (Just n2 : as) = n1 /= n2 || ruleCantMatch ts as
130 ruleCantMatch (t : ts) (a : as) = ruleCantMatch ts as
131 ruleCantMatch ts as = False
135 %************************************************************************
137 SpecInfo: the rules in an IdInfo
139 %************************************************************************
142 mkSpecInfo :: [CoreRule] -> SpecInfo
143 mkSpecInfo rules = SpecInfo rules (rulesRhsFreeVars rules)
145 extendSpecInfo :: SpecInfo -> [CoreRule] -> SpecInfo
146 extendSpecInfo (SpecInfo rs1 fvs1) rs2
147 = SpecInfo (rs2 ++ rs1) (rulesRhsFreeVars rs2 `unionVarSet` fvs1)
149 addSpecInfo :: SpecInfo -> SpecInfo -> SpecInfo
150 addSpecInfo (SpecInfo rs1 fvs1) (SpecInfo rs2 fvs2)
151 = SpecInfo (rs1 ++ rs2) (fvs1 `unionVarSet` fvs2)
153 addIdSpecialisations :: Id -> [CoreRule] -> Id
154 addIdSpecialisations id rules
155 = setIdSpecialisation id $
156 extendSpecInfo (idSpecialisation id) rules
158 rulesOfBinds :: [CoreBind] -> [CoreRule]
159 rulesOfBinds binds = concatMap (concatMap idCoreRules . bindersOf) binds
163 %************************************************************************
167 %************************************************************************
170 type RuleBase = NameEnv [CoreRule]
171 -- Maps (the name of) an Id to its rules
172 -- The rules are are unordered;
173 -- we sort out any overlaps on lookup
175 emptyRuleBase = emptyNameEnv
177 mkRuleBase :: [CoreRule] -> RuleBase
178 mkRuleBase rules = extendRuleBaseList emptyRuleBase rules
180 extendRuleBaseList :: RuleBase -> [CoreRule] -> RuleBase
181 extendRuleBaseList rule_base new_guys
182 = foldl extendRuleBase rule_base new_guys
184 unionRuleBase :: RuleBase -> RuleBase -> RuleBase
185 unionRuleBase rb1 rb2 = plusNameEnv_C (++) rb1 rb2
187 extendRuleBase :: RuleBase -> CoreRule -> RuleBase
188 extendRuleBase rule_base rule
189 = extendNameEnv_Acc (:) singleton rule_base (ruleIdName rule) rule
191 pprRuleBase :: RuleBase -> SDoc
192 pprRuleBase rules = vcat [ pprRules (tidyRules emptyTidyEnv rs)
193 | rs <- nameEnvElts rules ]
197 %************************************************************************
199 \subsection{Matching}
201 %************************************************************************
204 lookupRule :: (Activation -> Bool) -> InScopeSet
205 -> RuleBase -- Imported rules
206 -> Id -> [CoreExpr] -> Maybe (CoreRule, CoreExpr)
207 lookupRule is_active in_scope rule_base fn args
208 = matchRules is_active in_scope fn args rules
210 -- The rules for an Id come from two places:
211 -- (a) the ones it is born with (idCoreRules fn)
212 -- (b) rules added in subsequent modules (extra_rules)
213 -- PrimOps, for example, are born with a bunch of rules under (a)
214 rules = extra_rules ++ idCoreRules fn
215 extra_rules | isLocalId fn = []
216 | otherwise = lookupNameEnv rule_base (idName fn) `orElse` []
218 matchRules :: (Activation -> Bool) -> InScopeSet
220 -> [CoreRule] -> Maybe (CoreRule, CoreExpr)
221 -- See comments on matchRule
222 matchRules is_active in_scope fn args rules
223 = -- pprTrace "matchRules" (ppr fn <+> ppr rules) $
226 (m:ms) -> Just (findBest (fn,args) m ms)
228 rough_args = map roughTopName args
230 go :: [(CoreRule,CoreExpr)] -> [CoreRule] -> [(CoreRule,CoreExpr)]
232 go ms (r:rs) = case (matchRule is_active in_scope args rough_args r) of
233 Just e -> go ((r,e):ms) rs
234 Nothing -> -- pprTrace "Failed match" ((ppr r) $$ (ppr args)) $
237 findBest :: (Id, [CoreExpr])
238 -> (CoreRule,CoreExpr) -> [(CoreRule,CoreExpr)] -> (CoreRule,CoreExpr)
239 -- All these pairs matched the expression
240 -- Return the pair the the most specific rule
241 -- The (fn,args) is just for overlap reporting
243 findBest target (rule,ans) [] = (rule,ans)
244 findBest target (rule1,ans1) ((rule2,ans2):prs)
245 | rule1 `isMoreSpecific` rule2 = findBest target (rule1,ans1) prs
246 | rule2 `isMoreSpecific` rule1 = findBest target (rule2,ans2) prs
248 | otherwise = pprTrace "Rules.findBest: rule overlap (Rule 1 wins)"
249 (vcat [ptext SLIT("Expression to match:") <+> ppr fn <+> sep (map ppr args),
250 ptext SLIT("Rule 1:") <+> ppr rule1,
251 ptext SLIT("Rule 2:") <+> ppr rule2]) $
252 findBest target (rule1,ans1) prs
254 | otherwise = findBest target (rule1,ans1) prs
259 isMoreSpecific :: CoreRule -> CoreRule -> Bool
260 isMoreSpecific (BuiltinRule {}) r2 = True
261 isMoreSpecific r1 (BuiltinRule {}) = False
262 isMoreSpecific (Rule { ru_bndrs = bndrs1, ru_args = args1 })
263 (Rule { ru_bndrs = bndrs2, ru_args = args2 })
264 = isJust (matchN in_scope bndrs2 args2 args1)
266 in_scope = mkInScopeSet (mkVarSet bndrs1)
267 -- Actually we should probably include the free vars
268 -- of rule1's args, but I can't be bothered
270 noBlackList :: Activation -> Bool
271 noBlackList act = False -- Nothing is black listed
273 matchRule :: (Activation -> Bool) -> InScopeSet
274 -> [CoreExpr] -> [Maybe Name]
275 -> CoreRule -> Maybe CoreExpr
277 -- If (matchRule rule args) returns Just (name,rhs)
278 -- then (f args) matches the rule, and the corresponding
279 -- rewritten RHS is rhs
281 -- The bndrs and rhs is occurrence-analysed
286 -- forall f g x. map f (map g x) ==> map (f . g) x
288 -- CoreRule "map/map"
289 -- [f,g,x] -- tpl_vars
290 -- [f,map g x] -- tpl_args
291 -- map (f.g) x) -- rhs
293 -- Then the call: matchRule the_rule [e1,map e2 e3]
294 -- = Just ("map/map", (\f,g,x -> rhs) e1 e2 e3)
296 -- Any 'surplus' arguments in the input are simply put on the end
299 matchRule is_active in_scope args rough_args
300 (BuiltinRule { ru_name = name, ru_try = match_fn })
301 = case match_fn args of
302 Just expr -> Just expr
305 matchRule is_active in_scope args rough_args
306 (Rule { ru_name = rn, ru_act = act, ru_rough = tpl_tops,
307 ru_bndrs = tpl_vars, ru_args = tpl_args,
309 | not (is_active act) = Nothing
310 | ruleCantMatch tpl_tops rough_args = Nothing
312 = case matchN in_scope tpl_vars tpl_args args of
314 Just (binds, tpl_vals) -> Just (mkLets binds $
315 rule_fn `mkApps` tpl_vals)
317 rule_fn = occurAnalyseExpr (mkLams tpl_vars rhs)
318 -- We could do this when putting things into the rulebase, I guess
323 -> [Var] -- Template tyvars
324 -> [CoreExpr] -- Template
325 -> [CoreExpr] -- Target; can have more elts than template
326 -> Maybe ([CoreBind], -- Bindings to wrap around the entire result
327 [CoreExpr]) -- What is substituted for each template var
329 matchN in_scope tmpl_vars tmpl_es target_es
330 = do { (tv_subst, id_subst, binds)
331 <- go init_menv emptySubstEnv tmpl_es target_es
332 ; return (fromOL binds,
333 map (lookup_tmpl tv_subst id_subst) tmpl_vars) }
335 init_menv = ME { me_tmpls = mkVarSet tmpl_vars, me_env = init_rn_env }
336 init_rn_env = mkRnEnv2 (extendInScopeSetList in_scope tmpl_vars)
338 go menv subst [] es = Just subst
339 go menv subst ts [] = Nothing -- Fail if too few actual args
340 go menv subst (t:ts) (e:es) = do { subst1 <- match menv subst t e
341 ; go menv subst1 ts es }
343 lookup_tmpl :: TvSubstEnv -> IdSubstEnv -> Var -> CoreExpr
344 lookup_tmpl tv_subst id_subst tmpl_var
345 | isTyVar tmpl_var = case lookupVarEnv tv_subst tmpl_var of
347 Nothing -> unbound tmpl_var
348 | otherwise = case lookupVarEnv id_subst tmpl_var of
350 other -> unbound tmpl_var
352 unbound var = pprPanic "Template variable unbound in rewrite rule" (ppr var)
356 ---------------------------------------------
357 The inner workings of matching
358 ---------------------------------------------
361 -- These two definitions are not the same as in Subst,
362 -- but they simple and direct, and purely local to this module
364 -- * The domain of the TvSubstEnv and IdSubstEnv are the template
365 -- variables passed into the match.
367 -- * The (OrdList CoreBind) in a SubstEnv are the bindings floated out
368 -- from nested matches; see the Let case of match, below
370 type SubstEnv = (TvSubstEnv, IdSubstEnv, OrdList CoreBind)
371 type IdSubstEnv = IdEnv CoreExpr
373 emptySubstEnv :: SubstEnv
374 emptySubstEnv = (emptyVarEnv, emptyVarEnv, nilOL)
377 -- At one stage I tried to match even if there are more
378 -- template args than real args.
380 -- I now think this is probably a bad idea.
381 -- Should the template (map f xs) match (map g)? I think not.
382 -- For a start, in general eta expansion wastes work.
388 -> CoreExpr -- Template
389 -> CoreExpr -- Target
392 -- See the notes with Unify.match, which matches types
393 -- Everything is very similar for terms
395 -- Interesting examples:
397 -- \x->f against \f->f
398 -- When we meet the lambdas we must remember to rename f to f' in the
399 -- second expresion. The RnEnv2 does that.
402 -- forall a. \b->b against \a->3
403 -- We must rename the \a. Otherwise when we meet the lambdas we
404 -- might substitute [a/b] in the template, and then erroneously
405 -- succeed in matching what looks like the template variable 'a' against 3.
407 -- The Var case follows closely what happens in Unify.match
408 match menv subst (Var v1) e2
409 | Just subst <- match_var menv subst v1 e2
412 -- Here is another important rule: if the term being matched is a
413 -- variable, we expand it so long as its unfolding is a WHNF
414 -- (Its occurrence information is not necessarily up to date,
415 -- so we don't use it.)
416 match menv subst e1 (Var v2)
417 | not (inRnEnvR rn_env v2),
418 -- If v2 is in the RnEnvR, then it's locally bound and can't
419 -- have an unfolding. We must make this check because if it
420 -- is locally bound we must not look it up in the in-scope set
421 -- E.g. (\x->x) where x is already in scope
422 isCheapUnfolding unfolding
423 = match menv subst e1 (unfoldingTemplate unfolding)
426 unfolding = idUnfolding (lookupRnInScope rn_env v2)
427 -- Notice that we look up v2 in the in-scope set
428 -- See Note [Lookup in-scope]
430 -- Matching a let-expression. Consider
431 -- RULE forall x. f (g x) = <rhs>
432 -- and target expression
433 -- f (let { w=R } in g E))
434 -- Then we'd like the rule to match, to generate
435 -- let { w=R } in (\x. <rhs>) E
436 -- In effect, we want to float the let-binding outward, to enable
437 -- the match to happen. This is the WHOLE REASON for accumulating
438 -- bindings in the SubstEnv
440 -- We can only do this if
441 -- (a) Widening the scope of w does not capture any variables
442 -- We use a conservative test: w is not already in scope
443 -- (b) The free variables of R are not bound by the part of the
444 -- target expression outside the let binding; e.g.
445 -- f (\v. let w = v+1 in g E)
446 -- Here we obviously cannot float the let-binding for w.
448 match menv subst@(tv_subst, id_subst, binds) e1 (Let bind e2)
449 | all freshly_bound bndrs,
450 not (any locally_bound bind_fvs)
451 = match (menv { me_env = rn_env' })
452 (tv_subst, id_subst, binds `snocOL` bind)
456 bndrs = bindersOf bind
457 bind_fvs = varSetElems (bindFreeVars bind)
458 freshly_bound x = not (x `rnInScope` rn_env)
459 locally_bound x = inRnEnvR rn_env x
460 rn_env' = extendRnInScopeList rn_env bndrs
462 match menv subst (Lit lit1) (Lit lit2)
466 match menv subst (App f1 a1) (App f2 a2)
467 = do { subst' <- match menv subst f1 f2
468 ; match menv subst' a1 a2 }
470 match menv subst (Lam x1 e1) (Lam x2 e2)
471 = match menv' subst e1 e2
473 menv' = menv { me_env = rnBndr2 (me_env menv) x1 x2 }
475 -- This rule does eta expansion
476 -- (\x.M) ~ N iff M ~ N x
477 -- It's important that this is *after* the let rule,
478 -- so that (\x.M) ~ (let y = e in \y.N)
479 -- does the let thing, and then gets the lam/lam rule above
480 match menv subst (Lam x1 e1) e2
481 = match menv' subst e1 (App e2 (varToCoreExpr new_x))
483 (rn_env', new_x) = rnBndrL (me_env menv) x1
484 menv' = menv { me_env = rn_env' }
486 -- Eta expansion the other way
487 -- M ~ (\y.N) iff M y ~ N
488 match menv subst e1 (Lam x2 e2)
489 = match menv' subst (App e1 (varToCoreExpr new_x)) e2
491 (rn_env', new_x) = rnBndrR (me_env menv) x2
492 menv' = menv { me_env = rn_env' }
494 match menv subst (Case e1 x1 ty1 alts1) (Case e2 x2 ty2 alts2)
495 = do { subst1 <- match_ty menv subst ty1 ty2
496 ; subst2 <- match menv subst1 e1 e2
497 ; let menv' = menv { me_env = rnBndr2 (me_env menv) x1 x2 }
498 ; match_alts menv' subst2 alts1 alts2 -- Alts are both sorted
501 match menv subst (Type ty1) (Type ty2)
502 = match_ty menv subst ty1 ty2
504 match menv subst (Cast e1 co1) (Cast e2 co2)
505 | (from1, to1) <- coercionKind co1
506 , (from2, to2) <- coercionKind co2
507 = do { subst1 <- match_ty menv subst to1 to2
508 ; subst2 <- match_ty menv subst1 from1 from2
509 ; match menv subst2 e1 e2 }
511 {- REMOVING OLD CODE: I think that the above handling for let is
512 better than the stuff here, which looks
513 pretty suspicious to me. SLPJ Sept 06
514 -- This is an interesting rule: we simply ignore lets in the
515 -- term being matched against! The unfolding inside it is (by assumption)
516 -- already inside any occurrences of the bound variables, so we'll expand
517 -- them when we encounter them. This gives a chance of matching
518 -- forall x,y. f (g (x,y))
520 -- f (let v = (a,b) in g v)
522 match menv subst e1 (Let bind e2)
523 = match (menv { me_env = rn_env' }) subst e1 e2
525 (rn_env', _bndrs') = mapAccumL rnBndrR (me_env menv) (bindersOf bind)
526 -- It's important to do this renaming, so that the bndrs
527 -- are brought into the local scope. For example:
529 -- forall f,x,xs. f (x:xs)
531 -- f (let y = e in (y:[]))
532 -- We must not get success with x->y! So we record that y is
533 -- locally bound (with rnBndrR), and proceed. The Var case
534 -- will fail when trying to bind x->y
537 -- Everything else fails
538 match menv subst e1 e2 = -- pprTrace "Failing at" ((text "e1:" <+> ppr e1) $$ (text "e2:" <+> ppr e2)) $
541 ------------------------------------------
542 match_var :: MatchEnv
545 -> CoreExpr -- Target
547 match_var menv subst@(tv_subst, id_subst, binds) v1 e2
548 | v1' `elemVarSet` me_tmpls menv
549 = case lookupVarEnv id_subst v1' of
550 Nothing | any (inRnEnvR rn_env) (varSetElems (exprFreeVars e2))
551 -> Nothing -- Occurs check failure
552 -- e.g. match forall a. (\x-> a x) against (\y. y y)
554 | otherwise -- No renaming to do on e2
555 -> Just (tv_subst, extendVarEnv id_subst v1 e2, binds)
557 Just e2' | tcEqExprX (nukeRnEnvL rn_env) e2' e2
563 | otherwise -- v1 is not a template variable; check for an exact match with e2
565 Var v2 | v1' == rnOccR rn_env v2 -> Just subst
570 v1' = rnOccL rn_env v1
571 -- If the template is
572 -- forall x. f x (\x -> x) = ...
573 -- Then the x inside the lambda isn't the
574 -- template x, so we must rename first!
577 ------------------------------------------
578 match_alts :: MatchEnv
580 -> [CoreAlt] -- Template
581 -> [CoreAlt] -- Target
583 match_alts menv subst [] []
585 match_alts menv subst ((c1,vs1,r1):alts1) ((c2,vs2,r2):alts2)
587 = do { subst1 <- match menv' subst r1 r2
588 ; match_alts menv subst1 alts1 alts2 }
591 menv' = menv { me_env = rnBndrs2 (me_env menv) vs1 vs2 }
593 match_alts menv subst alts1 alts2
597 Matching Core types: use the matcher in TcType.
598 Notice that we treat newtypes as opaque. For example, suppose
599 we have a specialised version of a function at a newtype, say
601 We only want to replace (f T) with f', not (f Int).
604 ------------------------------------------
605 match_ty menv (tv_subst, id_subst, binds) ty1 ty2
606 = do { tv_subst' <- Unify.ruleMatchTyX menv tv_subst ty1 ty2
607 ; return (tv_subst', id_subst, binds) }
611 Note [Lookup in-scope]
612 ~~~~~~~~~~~~~~~~~~~~~~
613 Consider this example
614 foo :: Int -> Maybe Int -> Int
616 foo m (Just n) = foo (m-n) (Just n)
618 SpecConstr sees this fragment:
620 case w_smT of wild_Xf [Just A] {
621 Data.Maybe.Nothing -> lvl_smf;
622 Data.Maybe.Just n_acT [Just S(L)] ->
623 case n_acT of wild1_ams [Just A] { GHC.Base.I# y_amr [Just L] ->
624 $wfoo_smW (GHC.Prim.-# ds_Xmb y_amr) wild_Xf
627 and correctly generates the rule
629 RULES: "SC:$wfoo1" [0] __forall {y_amr [Just L] :: GHC.Prim.Int#
630 sc_snn :: GHC.Prim.Int#}
631 $wfoo_smW sc_snn (Data.Maybe.Just @ GHC.Base.Int (GHC.Base.I# y_amr))
632 = $s$wfoo_sno y_amr sc_snn ;]
634 BUT we must ensure that this rule matches in the original function!
635 Note that the call to $wfoo is
636 $wfoo_smW (GHC.Prim.-# ds_Xmb y_amr) wild_Xf
638 During matching we expand wild_Xf to (Just n_acT). But then we must also
639 expand n_acT to (I# y_amr). And we can only do that if we look up n_acT
640 in the in-scope set, because in wild_Xf's unfolding it won't have an unfolding
643 That is why the 'lookupRnInScope' call in the (Var v2) case of 'match'
647 %************************************************************************
649 \subsection{Checking a program for failing rule applications}
651 %************************************************************************
653 -----------------------------------------------------
655 -----------------------------------------------------
657 We want to know what sites have rules that could have fired but didn't.
658 This pass runs over the tree (without changing it) and reports such.
660 NB: we assume that this follows a run of the simplifier, so every Id
661 occurrence (including occurrences of imported Ids) is decorated with
662 all its (active) rules. No need to construct a rule base or anything
666 ruleCheckProgram :: CompilerPhase -> String -> [CoreBind] -> SDoc
667 -- Report partial matches for rules beginning
668 -- with the specified string
669 ruleCheckProgram phase rule_pat binds
671 = text "Rule check results: no rule application sites"
673 = vcat [text "Rule check results:",
675 vcat [ p $$ line | p <- bagToList results ]
678 results = unionManyBags (map (ruleCheckBind (phase, rule_pat)) binds)
679 line = text (replicate 20 '-')
681 type RuleCheckEnv = (CompilerPhase, String) -- Phase and Pattern
683 ruleCheckBind :: RuleCheckEnv -> CoreBind -> Bag SDoc
684 -- The Bag returned has one SDoc for each call site found
685 ruleCheckBind env (NonRec b r) = ruleCheck env r
686 ruleCheckBind env (Rec prs) = unionManyBags [ruleCheck env r | (b,r) <- prs]
688 ruleCheck :: RuleCheckEnv -> CoreExpr -> Bag SDoc
689 ruleCheck env (Var v) = emptyBag
690 ruleCheck env (Lit l) = emptyBag
691 ruleCheck env (Type ty) = emptyBag
692 ruleCheck env (App f a) = ruleCheckApp env (App f a) []
693 ruleCheck env (Note n e) = ruleCheck env e
694 ruleCheck env (Cast e co) = ruleCheck env e
695 ruleCheck env (Let bd e) = ruleCheckBind env bd `unionBags` ruleCheck env e
696 ruleCheck env (Lam b e) = ruleCheck env e
697 ruleCheck env (Case e _ _ as) = ruleCheck env e `unionBags`
698 unionManyBags [ruleCheck env r | (_,_,r) <- as]
700 ruleCheckApp env (App f a) as = ruleCheck env a `unionBags` ruleCheckApp env f (a:as)
701 ruleCheckApp env (Var f) as = ruleCheckFun env f as
702 ruleCheckApp env other as = ruleCheck env other
706 ruleCheckFun :: RuleCheckEnv -> Id -> [CoreExpr] -> Bag SDoc
707 -- Produce a report for all rules matching the predicate
708 -- saying why it doesn't match the specified application
710 ruleCheckFun (phase, pat) fn args
711 | null name_match_rules = emptyBag
712 | otherwise = unitBag (ruleAppCheck_help phase fn args name_match_rules)
714 name_match_rules = filter match (idCoreRules fn)
715 match rule = pat `isPrefixOf` unpackFS (ruleName rule)
717 ruleAppCheck_help :: CompilerPhase -> Id -> [CoreExpr] -> [CoreRule] -> SDoc
718 ruleAppCheck_help phase fn args rules
719 = -- The rules match the pattern, so we want to print something
720 vcat [text "Expression:" <+> ppr (mkApps (Var fn) args),
721 vcat (map check_rule rules)]
724 i_args = args `zip` [1::Int ..]
725 rough_args = map roughTopName args
727 check_rule rule = rule_herald rule <> colon <+> rule_info rule
729 rule_herald (BuiltinRule { ru_name = name })
730 = ptext SLIT("Builtin rule") <+> doubleQuotes (ftext name)
731 rule_herald (Rule { ru_name = name })
732 = ptext SLIT("Rule") <+> doubleQuotes (ftext name)
735 | Just _ <- matchRule noBlackList emptyInScopeSet args rough_args rule
736 = text "matches (which is very peculiar!)"
738 rule_info (BuiltinRule {}) = text "does not match"
740 rule_info (Rule { ru_name = name, ru_act = act,
741 ru_bndrs = rule_bndrs, ru_args = rule_args})
742 | not (isActive phase act) = text "active only in later phase"
743 | n_args < n_rule_args = text "too few arguments"
744 | n_mismatches == n_rule_args = text "no arguments match"
745 | n_mismatches == 0 = text "all arguments match (considered individually), but rule as a whole does not"
746 | otherwise = text "arguments" <+> ppr mismatches <+> text "do not match (1-indexing)"
748 n_rule_args = length rule_args
749 n_mismatches = length mismatches
750 mismatches = [i | (rule_arg, (arg,i)) <- rule_args `zip` i_args,
751 not (isJust (match_fn rule_arg arg))]
753 lhs_fvs = exprsFreeVars rule_args -- Includes template tyvars
754 match_fn rule_arg arg = match menv emptySubstEnv rule_arg arg
756 in_scope = lhs_fvs `unionVarSet` exprFreeVars arg
757 menv = ME { me_env = mkRnEnv2 (mkInScopeSet in_scope)
758 , me_tmpls = mkVarSet rule_bndrs }